Forged steel 1350 series slip yoke for 32-spline TH400 output shafts, replacing 3-3-2431X and also fitting 4L80E, 4L85E and Muncie M21/M22.
Leaking out the back of a Turbo 400 or 4L80E, building a TH400 for more power and bigger tires, or moving a driveshaft up from a 1310 to a 1350 joint? This is a forged steel 1350 series slip yoke for GM's 32-spline output shaft, the 3-3-2431X pattern. It fits the TH400, 4L80E and 4L85E automatics, plus Muncie M20, M21 and M22, Richmond, Jericho and Borg Warner Super T10 manual transmissions that use the 32-spline output.
The slip yoke is the front of the driveshaft. Its internal splines slide over the transmission output shaft, and its machined outside barrel rides in the tailhousing bushing and against the rear seal. As the rear axle moves up and down, the yoke slides in and out of the tailhousing so the driveshaft length can change without binding. That barrel is also a sealing surface: the rear seal lip rides on it, so a yoke with a worn groove or pitting leaks no matter how many seals you install. On the other end, the 1350 cross and ears carry torque to the shaft. The 1350 joint has a 1.188 inch cap against the smaller cap of a 1310, which is why builders move to 1350 when torque or tire size goes up.
With the truck on the ground, grab the driveshaft right behind the tailhousing and try to move it up and down. Noticeable play points to a worn bushing, not just a worn yoke. Pull the shaft, wipe the yoke barrel clean, and run a fingernail across the seal track. If it catches, replace the yoke. On a 4L80E truck with a vibration complaint, rule out the drivetrain before chasing shift problems; our 4L80E common problems and fixes guide covers what is actually internal. A yoke that has been leaking for a long time also means low fluid, so check the level and condition as described in the Silverado 2500 4L80E problems guide.
Key dimensions: 1350 series, outside snap ring style U-joint (5-1350X), 32-spline with a 1.378 inch spline OD, 1.885 inch hub diameter where the seal rides, 3.625 inch U-joint width, and 5.500 inch overall length. The listing cross-references 3-3-2431X, N3-3-2431X, T3-3-2431CBH and T3-3-2431CBHP. Be careful with those last two. Sonnax builds the CBH for tailhousings with a roller bearing instead of a bushing, and the CBHP with a counterbore for output shafts that are threaded on the end. If your old yoke has a counterbore, or your tailhousing uses a roller bearing, measure it against these numbers first. Count the splines on the output shaft, not on a worn yoke. On 4L80E trucks, only 2WD models use a slip yoke; 4x4 trucks bolt the transmission to a transfer case. Send us your measurements or year and VIN if you want us to check it, and browse more 4L80E parts in our 4L80E collection.
Top up with the right fluid after a leak. A rear leak on a 4L80E often goes unnoticed until the level is low, so a fresh ATP TF-174 filter kit and new fluid is cheap insurance. If you are building a big block TH400, the SFI 168-tooth 454 flexplate belongs on the same list, and a 4L80E shift kit firms up shifts for towing.
| Series | 1350, outside snap ring style |
| Spline | 32 spline (31/32), spline OD 1.378 in |
| U-joint cap diameter | 1.188 in |
| U-joint width | 3.625 in |
| Hub diameter | 1.885 in |
| Overall length | 5.500 in |
| Replaces | 3-3-2431X, N3-3-2431X, T3-3-2431CBH, T3-3-2431CBHP |
| Material | Forged steel |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
Yes. The 4L80E and 4L85E use the same 32-spline output pattern as the TH400. Only 2WD 4L80E trucks use a slip yoke; 4x4 models bolt to a transfer case and do not.
A 1350 series outside snap ring style U-joint, number 5-1350X. The 1350 cap diameter is 1.188 inches.
The seal rides on the yoke barrel. If the barrel has a worn groove, or the tailhousing bushing is worn and lets the yoke move around, the new seal leaks again. Replace the yoke and check the bushing together.
Those setups use special yokes. Sonnax makes a counterbore version for threaded shafts and a roller bearing version. If your old yoke has a counterbore or your tailhousing uses a roller bearing, measure your original against our listed dimensions or send us photos before ordering.
Measure the overall length from the U-joint centerline to the end of the barrel, the barrel diameter where the seal rides, and the U-joint cap size and width. Count the output shaft splines. This yoke is 5.500 inches long with a 1.885 inch hub, 32 splines and a 1350 joint.
